Solutions of metal-comprising materials, methods of forming metal-comprising layers, methods of storing metal-comprising materials, and methods of forming capacitors

ABSTRACT

In one aspect, the invention encompasses a semiconductor processing method of forming a metal-comprising layer over a substrate. A substrate is provided within a reaction chamber, and a source of a metal-comprising precursor is provided external to the reaction chamber. The metal-comprising precursor comprises a metal coordinated with at least one Lewis base to form a complex having a stoichiometric ratio of the at least one Lewis base to the metal. An amount of the at least one Lewis base is distributed within the source to an amount that is in excess of the stoichiometric ratio. At least some of the metal-comprising precursor is transported from the source to the reaction chamber. A metal is deposited from the metal-comprising precursor and onto the substrate within the reaction chamber. In another aspect, the invention encompasses a method of storing a metal-comprising material. A metal-comprising material is dispersed within a solution. The metal-comprising material comprises a complex having the stoichiometric form (Y) x M(Q) z ; wherein M is a metal, Y is a first ligand, x is from 0 to 4, Q is a Lewis base, and z is from 1 to 6. An amount of Q is dispersed within the solution to an excess over the stoichiometric ratio of Q to M in the complex.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.09/253,307, which was filed on Feb. 19, 1999, now U.S. Pat. No.6,319,832, and which is incorporated by reference herein.

TECHNICAL FIELD

In one aspect, the invention pertains to methods of formingsemiconductor circuit constructions, such as, for example, methods offorming capacitor constructions. In particular embodiments, theinvention pertains to methods of forming capacitor constructionscomprising diffusion barrier layers. In other aspects, the inventionpertains to solutions of metal-comprising materials, and to methods ofstoring metal-comprising materials.

BACKGROUND OF THE INVENTION

As DRAMs increase in memory cell density, there is a continuingchallenge to maintain sufficiently high storage capacitance despite thecontinuing goal to further decrease cell area. One principal way ofincreasing cell capacitance is through cell structure techniques. Suchtechniques include three-dimensional cell capacitors, such as trenchedor stacked capacitors. Yet as feature size continues to become smallerand smaller, development of improved materials for cell dielectrics aswell as the cell structure are important. The feature size of 256 MbDRAMs is on the order of 0.25 micron, and conventional dielectrics suchas SiO₂ and Si₃N₄ might not be suitable because of small dielectricconstants.

Chemical vapor deposited oxide films, such as, for example tantalumoxide (Ta₂O₅), BaTiO₃ and SrTiO₃ films are considered to be verypromising cell dielectric layers. For instance, the dielectric constantof Ta₂O₅ is approximately three times that of Si₃N₄. Capacitorconstructions have been proposed and fabricated to include the use ofone or more of the oxide materials as a capacitor dielectric layer.However, diffusion relative to the oxide materials can be problematic inthe resultant capacitor constructions. For example, tantalum from Ta₂O₅tends to undesirably out-diffuse from dielectric layers comprisingtantalum oxide. Further, materials from the adjacent conductivecapacitor plates can diffuse into the tantalum-comprising dielectriclayers. In either event, the dielectric properties of the dielectriclayer are adversely affected in a less than predictable or anuncontrollable manner.

A method of inhibiting diffusion between tantalum oxide and adjacentmaterials is to surround the tantalum oxide with a material thatconstitutes a diffusion barrier layer. Suitable materials forutilization as diffusion barrier layers are materials comprisingtransition metals (such as, for example, ruthenium, osmium, rhodium,iridium and cobalt), and can include transition metal oxides (such as,for example, ruthenium oxide, osmium oxide, rhodium oxide, iridium oxideand cobalt oxide). The transition metals are typically deposited bychemical vapor deposition (CVD) utilizing metal-comprising precursorcompounds. The metal-comprising precursor compounds generally comprise atransition metal coordinated with one or more Lewis base ligands in theform of a complex. Exemplary metal-comprising precursors are(cyclopentadienyl)Rh(CO)₂, and (1,3-cyclohexadiene)Ru(CO)₃. During a CVDprocess, the metal-comprising precursors are provided in a reactionchamber with a substrate and subjected to temperature and pressureconditions (and, in some instances, to a plasma or photolysis) todecompose the precursor and cause release of metal from the precursor.The released metal is then deposited on the substrate. A difficulty inutilizing the above-describe metal-comprising precursors in CVDprocesses is that the precursors frequently decompose prematurely. Suchdecomposition can occur while the precursors are stored outside thechamber and can result in formation of dimers or molecular clusters ofthe transition metal precursors. The resulting materials comprisingdimers or molecular clusters are generally less volatile than are theoriginal metal-comprising precursors, and accordingly can be difficultto utilize in CVD processes. It would be desirable to develop methodsfor CVD of metal-comprising precursors which avoid the above-describeddifficulties.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a semiconductor processingmethod of forming a metal-comprising layer over a substrate. A substrateis provided within a reaction chamber, and a source of ametal-comprising precursor is provided external to the reaction chamber.The metal-comprising precursor comprises a metal coordinated with atleast one Lewis base to form a complex having a stoichiometric ratio ofthe Lewis base to the metal. An amount of the Lewis base is providedwithin the source to an excess of the stoichiometric ratio. At leastsome of the metal-comprising precursor is transported from the source tothe reaction chamber. A metal is deposited from the metal-comprisingprecursor and onto the substrate within the reaction chamber.

In another aspect, the invention encompasses a method of storing ametal-comprising material. A metal-comprising material is dispersedwithin a solution. The metal-comprising material comprises a complexhaving the stoichiometric form (Y)_(x)M(Q)_(z); wherein M is a metal, Yis a first ligand, x is from 0 to 4, Q is a Lewis base, and z is from 1to 6. An amount of Q is dispersed within the solution to an excess overthe stoichiometric ratio of Q to M in the complex.

In yet another aspect, the invention encompasses a method of forming acapacitor. A first capacitor electrode is formed over a substrate. Adiffusion barrier layer is formed proximate the first capacitorelectrode. A dielectric layer is formed. The dielectric layer isseparated from the first capacitor electrode by the diffusion barrierlayer. A second capacitor electrode is formed. The second capacitorelectrode is separated from the first electrode by the dielectric layer.The forming the diffusion barrier layer comprises the following steps.The substrate having the first capacitor electrode thereover is providedto within a reaction chamber. A source of a metal-comprising precursoris provided external to the reaction chamber. The metal-comprisingprecursor comprises a metal coordinated with one or more Lewis bases toform a complex having a stoichiometric ratio of the Lewis bases to themetal. At least some of metal-comprising precursor in the source is aliquid. A gas is provided, and an amount of at least one of the Lewisbases is distributed within the gas. After the Lewis base is distributedwithin the gas, the gas is passed through the liquid metal-comprisingprecursor of the source. At least some of the metal-comprising precursorfrom the source is transported to the reaction chamber with the gas. Ametal-containing film is deposited from the metal-comprising precursoronto the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is diagrammatic, sectional view of a reaction chamber systemconfigured in accordance with an aspect of the present invention.

FIG. 2 is a fragmentary, diagrammatic, sectional view of a semiconductorwafer fragment in accordance with an aspect of the invention.

FIG. 3 is a diagrammatic, sectional view of an alternate embodimentsemiconductor wafer fragment in accordance with an aspect of theinvention.

FIG. 4 is a diagrammatic, sectional view of yet another alternateembodiment semiconductor wafer fragment in accordance with an aspect ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

In one aspect, the invention encompasses an improved method for forminga metal-comprising layer over a substrate. The metal-comprisingprecursor includes complexes wherein metal atoms are coordinated withone or more Lewis bases. The ratio of the molar amount of Lewis baseligands bound in complexes with metal to the molar amount of metal boundin such complexes is referred to herein as a stoichiometric ratio. Themetal-comprising precursor is provided within a source vessel whichfurther includes an amount of the Lewis base distributed therein that isin excess of the stoichiometric ratio. The excess Lewis base reduces arate of decomposition of the metal-comprising precursor. In an exemplaryapplication of the present invention, excess carbon monoxide was addedto a solution of tricarbonyl(1,3-cyclohexadiene)ruthenium (CHDR).Specifically, a gaseous mixture of carbon monoxide and helium wasbubbled through liquid CHDR, with the carbon dioxide being provided to5% (by volume) in the gaseous mixture. No signs of decomposition weredetected after 7 days at 45° C. A control solution to which excesscarbon monoxide was not added showed substantial decomposition of CHDRafter just five hours.

A proposed mechanism for the reduction in a metal-comprising precursordecomposition rate by a method of the present invention is as follows.First, it is recognized that a metal-comprising precursor can be subjectto the equilibria of equations 1, 2 and 3.

(Y)_(x)M(Q)_(z)≈(Y)_(x)M(Q)_((z−w))+Q_(w)  (1)

2((Y)_(x)M(Q)_((z−w)))≈(Y)_(g)M₂(Q)_((h))  (2)

(Y)_(x)M(Q)_((z))+(Y)_(x)M(Q)_((z−w))≈(Y)_(g)M₂(Q)_((h))  (3)

In equation 1, “M” is a metal, “Y” is a first ligand and “Q” is a Lewisbase. Exemplary stoichiometries include “x” being from 0 to 4 (inparticular aspects “x” is an integer from 0 to 4), “z” being from 1 to 6(in particular aspects “z” is an integer from 1 to 6), and “w” beingfrom 1 to 6 (in particular aspects “w” is an integer from 1 to 6). Theequilibrium of equation 1 interconverts an undissociatedmetal-comprising precursor ((Y)_(x)M(Q)_(z)) with a decomposed form((Y)_(x)M(Q)_((z−w))) of the metal-comprising precursor. The equilibriaof equations 2 and 3 form dimers or larger molecular clusters. Inequations 2 and 3, an exemplary value of “g” is “2x”, and exemplaryvalues of “h” are from “(2z−w)” to “2(z−w)”.

The dimers or molecular clusters of equations 2 and 3 can be lessvolatile than the starting metal-comprising precursor, and are thereforeundesired. In accordance with the present invention, the addition ofexcess Lewis base (for example, excess “Q”) to a solution comprising themetal-comprising precursor can reduce the equilibrium amount of dimersand molecular clusters. Specifically, addition of excess Lewis base to asource of metal-comprising precursor pushes equilibrium 1 to the left,to thereby reduce a concentration of decomposed precursor within thesource solution. The reduction in concentration of decomposed precursorreduces the amount of precursor involved in equilibria 2 and 3, andaccordingly avoids dimer and molecular cluster formation. Theabove-described mechanism for reduction in dimer and molecular clusterformation is provided to possibly assist a reader in understanding amethod of the present invention, and is not intended to limit the scopeof the invention except to the extent that the mechanism is explicitlyrecited in the claims that follow.

A specific method of the present invention is described with referenceto a CVD system 10 in FIG. 1. CVD system 10 comprises a reaction chamber12 having an inlet 14 and an outlet 16. A semiconductive wafer substrate18 is provided within chamber 12, and held by a wafer holder 20.

CVD system 10 further comprises a vessel 22 provided externally toreaction chamber 12. In the shown embodiment, vessel 22 contains aliquid 24 which comprises a metal-comprising precursor, and is thus asource of metal-comprising precursor. It is noted that the inventionencompasses other embodiments (not shown) wherein the precursor is asolid or gas. In the shown embodiment, the source 24 can be either asolution comprising the metal-comprising precursor or can be neatmetal-comprising precursor. The metal-comprising precursor includes ametal coordinated with one or more Lewis bases to form a complex havinga stoichiometric ratio of the Lewis bases to the metal. Themetal-comprising precursor can comprise, for example, a complex havingthe formula of (Y)_(x)M(Q)_(z) wherein “M” is the metal, “Y” is a firstligand and “Q” is a Lewis base. Exemplary stoichiometries include “x”being from 0 to 4, and “z” being from 1 to 6. In exemplary embodiments,metal “M” is a transition metal, and can comprise, for example, a metalselected from the group consisting of Ru, Os, Rh, Ir and Co. Also inexemplary embodiments, “Y” is a multidentate chelate, such as, forexample, cyclopentadienyl, 1,3-cyclohexadiene or derivatives ofcyclodienes (such as, for example, methyl cyclopentadienyl). Further inexemplary embodiments, “Q” is selected from the group consisting of COand NH₃. Alternatively, “Q” can comprise an organic material having adouble bond that joins a pair of carbon atoms.

The source 24 is preferably maintained at a temperature and pressuresufficient to enable the metal-comprising precursor to be volatilizedand transported by the gas flowing through source 24. The temperature ispreferably from about 0° C. to about 100° C., more preferably from about0° C. to about 50° C., and most preferably from about 20° to about 40°C. The pressure is preferably from about 0.1 to about 760 Torr, morepreferably from about 0.1 to about 100 Torr, and most preferably fromabout 0.5 to about 50 Torr.

A second vessel 26 is provided in system 10, and is a source of a gas.Second vessel 26 has an outlet 28 which leads to a passageway 30 fordirecting a gas from vessel 26 into source 24. The gas forms bubbles 32within the liquid and transports at least some of the metal-comprisingprecursor from source 24 into reaction chamber 12. Preferably, the gaswithin vessel 26 comprises at least one of Lewis bases coordinated inthe metal-comprising precursor within source 24. For instance, if themetal-comprising precursor is (cyclopentadienyl)Rh(CO)₂, or(1,3-cyclohexadiene)Ru(CO)₃, the gas preferably comprises CO.Accordingly, as the gas is flowed into vessel 22 it distributes COwithin source 24 to an amount in excess of the stoichiometric ratio ofCO in the metal-comprising precursor complex. The CO can be distributedhomogeneously throughout source 24, or can be distributed as aconcentration gradient within source 24. The metal-comprising precursorvapor that is transported into vessel 12 is subjected to temperature andpressure conditions suitable for depositing a layer comprising the metalonto substrate 18.

The gas in vessel 26 can consist essentially of components that areLewis base ligands in a metal-comprising precursor complex (for example,the gas can consist essentially of CO when the metal-comprisingprecursor includes CO ligands), or can comprise a mixture of componentsthat are Lewis base ligands and other gaseous components (such othercomponents can be, for example, so-called “inert” gases, such as argon,helium or nitrogen). Preferably, the concentration of the Lewis baseligand components within the gas mixture is from about 0.01% to about100%, more preferably from about 0.1% to about 5%, and most preferablyfrom about 1% to about 2% (wherein the percentages are volume percent).Also, the gas can comprise materials that include a particular Lewisbase, rather than, or in addition to, comprising the particular Lewisbase. For instance, if the Lewis base is CO, the gas can comprise RCO(wherein “R” is an organic group bonded to CO) instead of, or inaddition to, CO.

It is to be understood that the metal-comprising precursors can comprisemultiple different Lewis bases (for instance, the ligands identified as“Y” in the above-described precursors (Y)_(x)M(Q)_(z) can be Lewis baseligands). By different Lewis bases, it is meant Lewis bases havingdifferent chemical formulas from one another. In accordance with thepresent invention, if a metal-comprising precursor comprises multipledifferent Lewis bases, at least one of the Lewis bases will preferablybe distributed within the source to an amount in excess of thestoichiometric ratio of the Lewis base in the complex. In particularembodiments, more than one of the different Lewis bases can bedistributed to amounts in excess of the stoichiometric ratio of saidLewis bases in the metal-comprising precursor complex.

The method described above with reference to FIG. 1 can be utilized forforming barrier layers in capacitor constructions. Exemplary capacitorconstructions are described with reference to FIGS. 2-4. Referring toFIG. 2, a semiconductor wafer fragment 10 comprises a capacitorconstruction 25 formed by a method of the present invention. Waferfragment 10 comprises a substrate 12 having a conductive diffusion area14 formed therein. Substrate 12 can comprise, for example,monocrystalline silicon. To aid in interpretation of the claims thatfollow, the term “semiconductive substrate” is defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

An insulating layer 16, typically borophosphosilicate glass (BPSG), isprovided over substrate 12, with a contact opening 18 provided thereinto diffusion area 14. A conductive material 20 fills contact opening 18,with material 20 and oxide layer 18 having been planarized as shown.Material 20 might be any suitable conductive material, such as, forexample, tungsten or conductively doped polysilicon. Capacitorconstruction 25 is provided atop layer 16 and plug 20, and electricallyconnected to node 14 through plug 20.

Capacitor construction 25 comprises a first capacitor electrode 26 whichhas been provided and patterned over node 20. An example and preferredmaterial is conductively doped polysilicon, provided to a thickness ofabout 1,000 Angstroms (for a 256 Mb DRAM). A capacitor dielectric layer28 is provided over first capacitor electrode 26. Capacitor dielectriclayer 28 can comprise, for example, one or both of silicon oxide andsilicon nitride. Alternatively, capacitor dielectric layer 28 cancomprise Ta₂O₅, BaTiO₃ and/or SrTiO₃. An exemplary process fordepositing a layer 28 comprising Ta₂O₅ is low pressure chemical vapordeposition at 450° C. using Ta(OC₂H₅)₅ and oxygen as precursors.Ta(OC₂H₅)₅ can be vaporized at 170° C., and introduced into a reactorchamber using argon or another suitable carrier gas. Subsequently,densification can occur by rapid thermal annealing in a dry oxygenatmosphere at a temperature ranging from 700° C. to 900° C. Preferably,if first capacitor electrode 26 comprises polysilicon, a surface of thepolysilicon is cleaned by an in situ HF dip prior to provision of Ta₂O₅.Rapid thermal treatments can also be carried out immediately prior toTa₂O₅ deposition, such as at 900° C. for 60 seconds in O₂. An exemplarythickness for layer 28 in accordance with 256 Mb integration is 100 Å.

A diffusion barrier layer 30 is provided over dielectric layer 28.Diffusion barrier layer 30 comprises a metal and can be provided by CVDutilizing the CVD system and methods described above with reference toFIG. 1.

After formation of barrier layer 30, a second capacitor electrode 32 isformed over barrier layer 30 to complete construction of capacitor 25.Second capacitor electrode 32 can comprise constructions similar tothose discussed above regarding first capacitor electrode 26, and canaccordingly comprise, for example, conductively doped polysilicon.Diffusion barrier layer 30 preferably prevents components (such as, forexample, tantalum or oxygen) from diffusing from dielectric material 28and into electrode 32. If, for example, oxygen diffuses into asilicon-comprising electrode 32, it can undesirably form SiO₂, whichwill significantly reduce the capacitance of capacitor 25. Diffusionbarrier layer 30 can also prevent diffusion of silicon from metalelectrode 32 to dielectric layer 28.

FIG. 3 illustrates an alternate embodiment capacitor construction andmethod in accordance with the invention. Like numerals from FIG. 2 havebeen utilized where appropriate, with differences indicated by thesuffix “a”. Wafer fragment 10 a comprises a capacitor construction 25 adiffering from the construction 25 of FIG. 2 in provision of a barrierlayer 30 a between first electrode 26 and dielectric layer 28, ratherthan between dielectric layer 28 and second capacitor electrode 32.Barrier layer 30 a can comprise constructions identical to thosediscussed above with reference to FIG. 2.

FIG. 4 illustrates yet another alternate embodiment capacitorconstruction and method. Like numerals from FIG. 2 are utilized whereappropriate, with differences being indicated by the suffix “b”, or bydifferent numerals. Wafer fragment 10 b includes a capacitorconstruction 25 b having the first and second capacitor plate 26 and 32,respectively, of the first described embodiment. However, wafer fragment10 b differs from wafer fragment 10 of FIG. 2 in that wafer fragment 10b comprises a second barrier layer 40 in addition to the barrier layer30. Barrier layer 40 is provided between first capacitor electrode 26and dielectric layer 28, whereas barrier layer 30 is between secondcapacitor electrode 32 and dielectric layer 28. Barrier layer 40 can beformed by methods identical to those discussed above with reference toFIG. 2 for formation of barrier layer 30.

In the embodiments of FIGS. 2-4 the barrier layers are shown anddescribed as being distinct layers separate from the capacitorelectrodes. It is to be understood, however, that the barrier layers cancomprise conductive materials and can accordingly, in such embodiments,be understood to comprise at least a portion of the capacitorelectrodes. In particular embodiments an entirety of a capacitorelectrode can be comprised of conductive barrier layer materials.

Although the invention has been described above with reference tomethods of transporting a metal-comprising precursor to a reactionchamber (FIG. 1), it is to be understood that the invention also hasapplication to methods of storing metal-comprising materials.Specifically, a metal-comprising material which includes a metalcoordinated with at least one Lewis base ligand to form a complex havinga stoichiometric ratio of the Lewis base ligand to the metal can bestored in accordance with the present invention as follows. Themetal-comprising material is dispersed within a solution, and an amountof the Lewis base is also dispersed within the solution, with the amountof the Lewis base being provided to be in excess of the stoichiometricratio of Lewis base in the complex. The solution can be a mixturecomprising the metal-comprising material or can be a neat liquid of thematerial. In a particular aspect of the invention, the solution can be aliquid which is sealed in a gas-tight vessel. The gas-tight vessel canhave a head-space over the liquid, and the head-space can contain a gas.The excess Lewis base can be provided within the gas in the head-space,and the dispersing of the Lewis base into the solution can comprisediffusion of the Lewis base from the gas and into the liquid solution.Suitable Lewis bases for utilization in such method are gaseous Lewisbases such as, for example, CO and NH₃.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A semiconductor processing method of forming ametal-comprising layer over a substrate, comprising: providing asemiconductor substrate within a reaction chamber; providing a source ofa metal-comprising precursor in fluid communication with the reactionchamber, the metal-comprising precursor having a metal coordinated withone or more Lewis bases to form a complex having an undissociatedstoichiometric ratio of the one or more Lewis bases to the metal;providing at least one of the one or more Lewis bases within the sourceto a concentration in excess of the stoichiometric ratio; transportingat least some of the metal-comprising precursor from the source to thereaction chamber; and depositing metal from the metal-comprisingprecursor onto the semiconductor substrate within the reaction chamber.2. The method of claim 1 wherein at least some of metal-comprisingprecursor in the source is a liquid.
 3. The method of claim 1 wherein atleast one of the one or more the Lewis bases is CO.
 4. The method ofclaim 1 wherein at least one of the one or more Lewis bases comprisenitrogen.
 5. The method of claim 1 wherein the metal-comprisingprecursor comprises the complex (Y)_(x)M(Q)_(z); M being the metal; Ybeing a first ligand, and x being from 0 to 4; Q being the one or moreLewis bases, and z being from 1 to
 6. 6. The method of claim 5 wherein Qis selected from the group consisting of CO and NH₃.
 7. The method ofclaim 5 wherein Y is a multidentate chelate.
 8. The method of claim 5wherein Y is a diene.
 9. The method of claim 1 wherein themetal-comprising precursor comprises the complex (Y)_(x)M(CO)_(z),wherein M is the metal, wherein Y is a multidentate chelate, wherein xis from 0 to 4, wherein z is from 1 to 6, and wherein CO is the Lewisbase provided within the source to an amount in excess of thestoichiometric ratio of the CO in the complex.
 10. The method of claim 1wherein the metal-comprising precursor comprises the complex(cyclopentadienyl)Rh(CO)₂, and wherein CO is provided within the sourceto an amount in excess of the stoichiometric ratio of the CO in thecomplex.
 11. The method of claim 1 wherein the metal-comprisingprecursor comprises the complex (1,3-cyclohexadiene)Ru(CO)₃, and whereinCO is provided within the source to an amount in excess of thestoichiometric ratio of the CO in the complex.
 12. The method of claim 1wherein the metal is a transition metal.
 13. The method of claim 1wherein the metal is selected from the group consisting of Ru, Os, Rh,Ir and Co.
 14. A semiconductor processing method of forming ametal-comprising layer over a semiconductor substrate, comprising:providing a semiconductor substrate within a reaction chamber; providinga source of a metal-comprising precursor external to the reactionchamber, the metal-comprising precursor comprising a metal coordinatedwith one or more Lewis bases to form a complex having a stoichiometricratio of each of the Lewis bases to the metal, at least some of themetal-comprising precursor in the source being a liquid; providing a gashaving an amount of at least one of the Lewis bases therein; passing thegas through the liquid metal-comprising precursor of the source whilemaintaining the source at a temperature of from about 0° C. to about100° C.; transporting at least some of the metal-comprising precursorfrom the source to the reaction chamber with the gas; and depositingmetal from the metal-comprising precursor onto the semiconductorsubstrate within the reaction chamber.
 15. The method of claim 14wherein the at least one Lewis base is CO.
 16. The method of claim 14wherein the at least one Lewis base comprises nitrogen.
 17. The methodof claim 14 wherein the metal-comprising precursor comprises at leasttwo Lewis bases, wherein the at least two Lewis bases have differentchemical formulas from one another, and wherein only one of the at leasttwo Lewis bases is distributed within the source to an amount in excessof the stoichiometric ratio of said only one Lewis base in the complex.18. The method of claim 14 wherein the metal-comprising precursorcomprises the complex (Y)_(x)M(Q)_(z); Y being a first ligand, and xbeing from 0 to 4; Q being the at least one Lewis base, and z being from1 to
 6. 19. The method of claim 18 wherein Q is selected from the groupconsisting of CO and NH₃.
 20. The method of claim 18 wherein Y is amultidentate chelate comprising a diene.
 21. The method of claim 14wherein the metal-comprising precursor comprises the complex(cyclopentadienyl)Rh(CO)₂, and wherein CO is distributed within thesource to an amount in excess of the stoichiometric ratio of the CO inthe complex.
 22. The method of claim 14 wherein the metal-comprisingprecursor comprises the complex (1,3-cyclohexadiene)Ru(CO)₃, and whereinCO is the at least one Lewis base distributed within the source to anamount in excess of the stoichiometric ratio of the CO in the complex.23. The method of claim 14 wherein the at least one Lewis base comprisesa double bond that joins a pair of carbon atoms.
 24. The method of claim14 wherein the metal is a transition metal.
 25. The method of claim 14wherein the metal is selected from the group consisting of Ru, Os, Rh,Ir and Co.
 26. A method of forming a capacitor, comprising: forming aconductive diffusion barrier layer over a semiconductor substrate, theforming the diffusion barrier layer comprising: providing the substratewithin a reaction chamber; providing a source of a metal-comprisingprecursor external to the reaction chamber, the metal-comprisingprecursor comprising a metal coordinated with one or more Lewis bases toform a complex having a stoichiometric ratio of each of the Lewis basesto the metal; providing a gas, and distributing an amount of at leastone of the Lewis bases within the gas; after distributing the at leastone of the Lewis bases within the gas, transporting at least some of themetal-comprising precursor from the source to the reaction chamber withthe gas; and depositing metal from the metal-comprising precursor ontothe semiconductor substrate within the reaction chamber; forming adielectric layer against the diffusion barrier layer; and forming asecond capacitor electrode separated from the diffusion barrier layer bythe dielectric layer.